When formulating dried particulate products such as would be made in a fluid bed dryer (e.g. particles for use in washing compositions), two problems normally occur. The first problem is that of dusting. The method of manufacturing particles can create very fine powders which cause dermatologic effects when the product contains sensitizing agents (e.g. enzymes in a detergent granule). The second problem relates to the need to incorporate relatively high amounts of ingredients such as enzyme protecting agents, masking agents and scavengers (e.g. chlorine scavengers) into products for the purpose of binding ions which can inactivate an active ingredient in the particle. It would be desirable to use less of these types of materials or to use them without interfering with enzymes that may be present.
Many commercially useful enzymes are produced by microorganisms, particularly bacteria, yeast and filamentous fungi. These enzymes are especially useful in detergent and food applications. With the advent of biotechnology and recombinant DNA techniques, other enzymes from mammlian sources are produced recombinantly in microorganisms. When enzymes are produced in a microbial host they are usually either secreted directly into the fermentation both by the microorganism or released into the fermentation broth by lysing the cell. The enzyme can then be recovered from the broth in a soluble form by a number of techniques including filtration, centrifugation, membrane filtration, chromatography and the like. The dissolved enzyme can be converted to a dry form from a liquid using techniques such a precipitation, crystallization or spray-drying. A problem associated with dry enzyme preparations is that there is a high dust level associated with them, which can cause dermatologic distress to the manufacturer, consumer or any other person handling the enzyme. It has been a desire in the art to treat these dry enzymes so as to reduce the hazard of dusting. To control dusting and increase particle size, dry enzymes are often granulated by various means known by those skilled in the art.
Various enzyme formulations and processes for these preparations have been developed in an effort to alleviate the dusting problem. For example, German Patent No. 21 37 042 discloses a process in which an enzyme-containing formulation is extruded through a die onto the revolving plate of a spheronizing device to form sperical particles of the enzyme-containing formulations which are optionally coated with a material designed to prevent dusting.
In U.S. Pat. No. 4,087,368, there is disclosed an enzyme granule formulation in which rods or spheres of an enzyme in admixture with magnesium alkyl sulfate and ethylene oxide are provided.
U.S. Pat. No. 4,016,040 discloses a method for the preparation of free-flowing substantially dust-free, spherical enzyme-containing beads prepared by blending a powdered concentrate of the enzyme with a binder in molten form and spraying droplets of the blend through a spray nozzle into cool air to solidify the droplets and form the beads.
In U.S. Pat. No. 4,242,219, there is claimed a process for the preparation of enzyme-containing particles prepared by mixing the dry enzyme with a hydrophilic organic cohesive material, a building agent or a mixture regulating agent and mechanically dividing it into particles of the desired size and shape which are then coated with a water repellent material.
Another type of granular enzyme formulation is described in U.S. Pat. No. 4,009,076. This formulation is prepared by mixing the dry enzyme with a solid nonviable substance and optionally a cohesive organic material as binder to form an enzymatically active core. An enzyme slurry containing the cohesive organic material can be sprayed onto, for example, sodium tripolyphosphate in a mixer or an enzyme powder can be mixed with the sodium tripolyphosphate and the cohesive organic material sprayed onto it with subsequent extrusion through a die. The enzyme-containing granule is sprayed with an aqueous solution containing a plasticized organic resin, then dried.
A process is described in GDR Patent 0 151 598 in which sodium tripolyphosphate is sprayed with an aqueous fermentation broth and agglomerated in a cyclone apparatus. The agglomerates are removed from the cyclone apparatus while still wet and placed in a mechanical blender with a drying detergent formulation and intensively mixed.
In British Patent No. 1,483,591, there is described a process for coating water soluble or water dispersible particles, including enzyme particles, using a fluidized-bed reactor. This reference involves a dust-free coating technique for enzyme particles which have been granulated by other processes such as prilling or spheronizing.
In U.S. Pat. No. 4,689,297, there is described a method for preparing dust-free enzyme involving dissolving or suspending dry enzyme in solution to make a slurry of at least 30% w/w of the solids enzymes, spraying it on a hydratable core and then coating it with macromolecular material.
In PCT patent application 87/00057 there is described a detergent enzyme product with an enzyme core on which is an enteric coating. Such coatings are water soluble and dissolve readily at high pH's while resisting dissolution at low pH's.
Oxidant scavengers or enzyme protecting agents or masking agents can be included in washing compositions to bind free ions, compounds or the like, which may inactivate the enzyme or decrease its efficacy or otherwise interfere with the ability of the detergent or enzyme preparation.
It is desirable to produce improved dust free particles which can decrease or eliminate the need for scavengers, enzyme protecting agents, or masking agents and other such compounds or increase the effectiveness of enzymes in the presence of ions.